Support filling images in cells

[wangsongyan]

PR Details

Support filling images in cells

Description

Add Fill option in excelize.GraphicOptions to allow user filling images in cells.

Related Issue

Motivation and Context

How Has This Been Tested

Types of changes

• [ ] Docs change / refactoring / dependency upgrade
• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• [x] My code follows the code style of this project.
• [x] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [x] I have added tests to cover my changes.
• [x] All new and existing tests passed.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 99.30%. Comparing base (c349313) to head (4190a78). Report is 1 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1923 +/- ## ========================================== - Coverage 99.30% 99.30% -0.01% ========================================== Files 32 32 Lines 24989 24962 -27 ========================================== - Hits 24815 24788 -27 Misses 93 93 Partials 81 81 ``` | [Flag](https://app.codecov.io/gh/qax-os/excelize/pull/1923/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qax-os) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/qax-os/excelize/pull/1923/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qax-os) | `99.30% <100.00%> (-0.01%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qax-os#carryforward-flags-in-the-pull-request-comment) to find out more.

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